The subject matter disclosed herein relates to gas turbines and, more particularly, to measurements of various properties of components within gas turbines using deposited sensors.
Measurement of gas turbine hot gas path component (e.g., turbine) temperatures typically has provided a relatively good tool for design engineers to validate their component design models, usually during gas turbine testing. In known test methods, some selective component parts are “instrumented” by attaching thermocouples or other types of property measurement devices or sensors (e.g., strain gauges) at specific component locations, and metal temperatures or other component properties (e.g., strain) are acquired or sensed.
It is advantageous to have the sensing instrumentation located on the component at all times to acquire real time data during the entirety of gas turbine operation. Moreover, gas turbine hot gas path components such as turbine airfoils and nozzles typically have coatings on them, which creates a challenge for attaching the sensor lead wires to the sensor itself. The coatings are used to protect the underlying component substrate from the relatively high operating temperatures that the components are exposed to. Also, advances have been made in the field of depositing sensors onto the coated surfaces of the hot gas path components using, for example, a “direct-write” method (e.g., thermal spraying). However, difficulties exist in adequately attaching the sensor lead wires to the sensors deposited on the gas turbine components by these direct-write methods. Known resistance spot welding techniques tend to be relatively unreliable and also pose component access limitations. In addition, various types of conventional welding or brazing techniques create welds or brazes that may break or crack when subjected to, e.g., high temperatures—particularly, a wide range of temperatures and long term cycles.